It is a common requirement to reduce the electric power consumption for a liquid crystal display device used for a portable device such as a mobile phone because a battery is used for such a device. Therefore various kinds of methods for reduction of the electric power consumption have been developed and are disclosed in, for example, Patent Documents 1, 2 and 3.
Patent Document 1 discloses a display device provided with a switch group for distributing (demultiplexing) column voltages to be outputted from a column driving circuit and for outputting the demultiplexed column voltages to column electrodes of a pixel part, wherein non-overlap periods when all of control signals of switches becomes ‘low’ are provided to the display device and the timing of respective signals are stipulated so that the column voltages are changed in these periods. According to the device, the column voltages are changed in a state when the switches of the group are all in OFF state. Thus, a phenomenon in which a previous column voltage is once applied on the column electrodes is avoided and then the unnecessary voltage fluctuation is prevented and the increasing of the power consumption can be avoided in the display device.
Patent Document 2 discloses a display memory, a driver circuit, and a liquid crystal display device using the driver circuit which reduce the power consumption and enable quick plotting and eliminate a need of memory mapping. According to the display memory, the driver circuit, and the liquid crystal display device using the driver circuit, because the display memory is provided with two lines of read ports and one line of write port at both bit lines of the memory, a cell size can be greatly reduced compared to a case using a memory of normal dual ports and wiring resources and corresponding power consumption can be reduced.
Patent Document 3 discloses a driving device for a liquid crystal display device which can prevent consumption of unnecessary power by determining whether an image to be displayed is a moving image or a still image, and in the case of the still image, controlling supply of power to be applied to a memory which does not perform practical operation or other related devices.
[Patent Document 1]
JP Patent Kokai Publication No. JP-P2003-255904A
[Patent Document 2]
JP Patent Kokai Publication No. JP-P2003-108056A
[Patent Document 3]
JP Patent Kokai Publication No. JP-P2004-272270A